E.D.
Teresa,
Try laying down a piece of wax paper over the water mark,then a thin towel or old t-shirt, and then putting a medium hot iron (no steam) on it for 10-15 seconds. My mom's coffee table had horrible water marks from glasses being set down without coasters, and it got them out like a charm. I learned this trick from a furniture-restorer, and he says that the wax protects your finish and the heat from the iron dries out the water that's embedded in the stain.
Good luck!
E.